Seasonal Climate Outlook Message for October to January 2005

The bottom line

Following some remarkable fluctuations earlier this year, the 30 day average of the SOI appears to have stabilized for now and as of the 12th October is minus 3.9.

Based on the current SOI phase and available rainfall records, there is a 40 to 50% chance of getting above median rainfall through to the end of December across much of Queensland. However, especially for parts of the north and west of the state there is only a 30 to 40% chance of getting above median rainfall through to the end of December.

For example, Emerald has a 35% chance of getting above its long-term October to December median rainfall of 175 mm, Charters Towers has a 38% chance of getting above its October to December median rainfall of 130 mm, Roma has a 40% chance of getting above its October to December median rainfall of 165 mm, and Dalby has a 55% chance of getting above its October to December median rainfall of 210 mm.

The full story

Rainfall probabilities for October to December (11/10/04)

Based on the shift in value of the SOI from the end of August (-6.7) to the end of September (-3.2) the SOI is in a "Consistently Near Zero" phase. This is the second month in a row the SOI has remained in a "Consistently Near Zero" phase.

Based on the current SOI phase and the available historical rainfall records for Queensland, there is a 40 to 50% chance of getting above median rainfall through to the end of December across most of Queensland. However, especially in the north and west of the state there are some areas that have a lower 30 to 40% chance of getting above median rainfall through to the end of December.

For example, Emerald has a 35% chance of getting above its long-term October to December median rainfall of 175 mm, Charters Towers has a 38% chance of getting above its October to December median rainfall of 130 mm, Roma has a 40% chance of getting above its October to December median rainfall of 165 mm, and Dalby has a 55% chance of getting above its October to December median rainfall of 210 mm.

Following some remarkable fluctuations earlier this year, the 30 day average of the SOI appears to have stabilized for now and as of the 7th October is minus 1.9. Daily updates on the SOI are available on (07) 46881439. For there to be an overall improvement in the seasonal outlook for Queensland, it would help if the SOI rose to a "Consistently Positive" pattern for a couple of months at least.

* Other states

Similar to rainfall probabilities in Queensland, there is a 30 to 60% chance of getting above the long-term October to December median rainfall across the rest of Australia. The higher rainfall probabilities (50-60%) can be found along the southern coast of Western Australia, the northeast quarter of South Australia and along the New South Wales and Victorian border. The latest rainfall probability maps for Queensland, Australia and the world are at www.dpi.qld.gov.au/climate or www.longpaddock.qld.gov.au

Because rainfall probabilities and median rainfall levels vary between regions, we recommend referring to Rainman StreamFlow for more specific information. Otherwise call the DPI Call Centre on 13 25 23 or (07) 3404 6999. This forecast doesn't indicate the potential distribution or expected timing of rainfall over this period. The forecast is for a full 3 month period and doesn't suggest that any expected rain will fall evenly across these 3 months.

* Understanding probabilities

As with any probability based forecast system it is important to consider the opposite aspect. For example Emerald currently has a 35% chance of getting above its long-term October to December median rainfall of 175 mm. This also means that there is a 65% chance of NOT getting the 175 mm through to the end of December.

Another way of looking at this is in around 3 years out of 10 (or around one third) with the current SOI pattern, Emerald has received at least 175 mm for October to December. Therefore in around 7 years out of 10 (or two thirds), Emerald has gotten less than 175 mm for October to December.

When interpreting rainfall probabilities for your area it may make it easier to think of them in these terms:

T he MJO is simply a band of low air pressure originating off the east coast of central Africa travelling eastward across the Indian Ocean and northern Australia roughly every 30 to 60 days. Research has shown the MJO to be a useful indicator of the timing of potential rainfall events across much of Queensland. The last active phase of the MJO across Australia occurred in early October unfortunately triggering little rain. If its timing remains current it will next be expected in mid November.

Given the growing interest in the MJO, and with funding from the DPI&F, GRDC and CRDC we have developed a site www.apsru.gov.au/mjo/ that will allow anyone interested to track its passage.

* Future ENSO development

As mentioned earlier, although we are not in a clearly defined El Niño event, sea surface temperatures (SST) in the central Pacific from the international dateline running east towards South America are warmer than normal (+0.5 to 1.5 degree C). We are describing the current SST pattern as a "border line El Niño". The USA Climate Prediction Centre www.cpc.ncep.noaa.gov/ expect this pattern to continue into early 2005.

While the current SST pattern is not usually as serious as the El Niño SST pattern such as occurred between 2002 and 2003, it can still have major impact on Queensland rainfall and water supply, especially if the SOI where to return to a "Consistently Negative SOI Phase". As an example, we had a borderline El Niño state in 1992 and 1993, both years producing below average rainfall for large parts of Queensland but not to the extent of the 2002/2003 event. The Bureau of Meteorology "El Niño wrap up" www.bom.gov.au/climate/enso/ is a good starting point to find out more on conditions in the Pacific.

For the latest sea surface temperature maps have a look at www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina or at www.longpaddock.qld.gov.au/

* Wheat Crop Yield Outlook

The current wheat outlook for Queensland as a whole shows a final forecast yield at the end of September of 1.12 t/ha. This is 19% below the long-term median of 1.39 t/ha.

Final yields vary greatly throughout the state. For central and southeast Queensland, there are below average crop yield expectations with some regions falling in the worst 10% of all years. However for parts of the far southwest and southwest crop yield expectations are closer to normal. With maturity being reached for almost all of the planted crops in Queensland, projected rainfall for the remainder of the growing season will have little to no effect on the final realised yield.

This wheat yield outlook is based on a shire scale. It does not take into account crop area planted and is purely a yield forecast. Nor does not take into account individual property circumstances or the effects and damage from poor crop nutrition, pests, diseases, frosts and distribution of planting rain within a shire. For more information on the APSRU/DPI&F regional wheat crop outlook contact Andries Potgieter on (07) 46881417 or try www.dpi.qld.gov.au/climate where a full copy the wheat crop outlook can be found.

Many people like to follow the relationship between the SOI and rainfall patterns in more detail. To do that, have a look at what happened in your area over October to December in the following years; 2003, 1999, 1995, 1992, 1986, 1985, 1984, 1980, 1978, 1968, 1966, 1963, 1961, 1959 and 1952 and compare the rainfall recorded with your 'normal' rainfall for October to December.

For example, during October to December at Dalby in those years, above average rainfall was recorded 8 times, near average rainfall was recorded 4 times and below average rainfall was recorded 3 times. At Emerald, above average rainfall was recorded 4 times, near average rainfall was recorded 3 times and below average rainfall was recorded 8 times.

Information on what rainfall patterns where like for October to December in those years can be found at www.longpaddock.qld.gov.au or in Australian Rainman.

* Recent Rainfall Trends

Below average rainfall has been recorded across most of Queensland over the last 3 years. It is interesting to see if this is just a short-term phenomenon before seasons return to what many would like to consider "normal" or, part of a longer-term trend. To estimate rainfall patterns in Australia over the last two to three hundred years, sources of information such as the annual florescence in cores of coral in the Great Barrier Reef and Pacific are measured. These cores suggest that over the past 245 years up to 2001, the 5 wettest years in order were 1887, 1974, 1755, 1768 and 1890 while the driest were 1902, 1867, 1812, 1823 and 1865.

Official rainfall records though are available for most locations in Australia from around the mid to late 1800's. Even over this short period there have been significant variations in rainfall (and temperature) over large parts of Australia.

For an example, Gayndah has 134 years of rainfall records and a long-term average annual rainfall of 766 mm. However using a 10 year moving average it becomes apparent that there have been prolonged periods of above and below the long-term average annual rainfall of 766 mm.

The highest 10 year moving average rainfall was 953 mm in 1956. Since this peak, the 10 year moving average rainfall at Gayndah has fallen to 672 mm at the end of 2003. This is a shift of around 280 mm (or approximately 11 inches). This downward trend since the mid 1950's is evident over much of eastern Australia and especially in Queensland. Rainfall trend maps are at www.bom.gov.au/silo/products/cli_chg/

This downward trend in rainfall patterns across most of the state is part of the reason we recommend getting updated accurate information on rainfall levels for your location. This will not only help interpret seasonal outlooks but provide a more realistic picture of what rainfall may be expected. This is important when developing management strategies and especially when considering large capital investments such as purchasing property.

* Key Points To Consider When Using Climate Information

When incorporating climate forecasts into management decisions, it could be worthwhile to consider some of the following general rules of thumb developed from feedback from climate users.

1. Be sure of your source of information and what it is actually suggesting. Do not take a quick grab of information from any source including radio, TV or the internet and assume what you heard/saw/read applies to your location.

2. Management decisions should never be based entirely on one factor (such as a weather or climate forecast). As always, all factors that could impact of the outcome of a decision (such as soil moisture/type, crop, pasture type/availability, commodity prices, machinery, work force, transport, finance, costs, seasonal outlook etc) should be considered.

3. Try to access local information or at least be aware of the long-term median for your location so you can correctly interpret the forecast.

4. Do a cost benefit analysis of any decision with a climate risk factor eg What will I gain if I get the desired outcome from this decision? What will I lose if I don't get the desired outcome from this decision? What other cost neutral options do I have if any?

5. Do not to take a forecast for a specific period (eg September to November) and expand it out (eg late summer). Update the information regularly.

An interesting site http://www.cvap.gov.au/mastersoftheclimate/ from the 'Climate Variability In Agriculture' (CVAP) research and development program is well worth looking at. It highlights some case studies on how producers and businesses have used (to varying levels of success) climate and weather information in their decision making processes.